Pharmaceutical formulations comprising 9-cis-retinyl esters in a lipid vehicle

ABSTRACT

Pharmaceutical formulations comprising 9-cis-retinyl esters in a lipid vehicle are described as retinoid replacement therapies for treating retinal degenerations in humans.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 15/274,257, filed Sep. 23, 2016, which is a divisional of U.S. application Ser. No. 13/496,113, filed Mar. 14, 2012, which is a national stage application under 35 U.S.C. § 371 of International Application No. PCT/US2009/059126, filed Sep. 30, 2009, which claims the benefit of U.S. Patent Application No. 61/242,741, filed Sep. 15, 2009, under 35 U.S.C. § 119(e), which is incorporated herein by reference in its entirety. International Application PCT/US2009/059126 was published under PCT Article 21(2) in English.

BACKGROUND Technical Field

This disclosure is related to pharmaceutical formulations comprising artificial retinoids, in particular, to stable formulations and dosage formulations suitable for visual chromophore replacement therapy.

Description of the Related Art

Visual perception results from a biological conversion of light energy into electrical signaling by retinal photoreceptors in the eye, a process called phototransduction. The phototransduction process is initiated by visual pigments, including the chromophore 11-cis-retinal bound to apoprotein G protein-coupled receptor opsins to form rhodopsin (Palczewski K. G protein-coupled receptor rhodopsin. Annual review of biochemistry 2006; 75:743-767). The chromophore absorbs photons, which triggers photoisomerization of the chromophore into its trans form and leads to signal transduction cascades (Palczewski K. supra; Ridge K D et al. Visual rhodopsin sees the light: structure and mechanism of G protein signaling. J Biol Chem 2007; 282:9297-9301). The isomerized chromophore, all-trans-retinal, is then reduced to all-trans-retinol, transported to the retina pigmented epithelium (RPE), and converted to fatty acid all-trans-retinyl esters by lecithin:retinol acyltransferase (LRAT). Finally, regeneration of 11-cis-retinal from the fatty acid all-trans-retinyl esters completes this retinoid (visual) cycle (see, e.g., U.S. Published Application Nos. 2004/0242704, 2006/028182, 2006/0221208).

Regeneration of 11-cis-retinal is critical for maintaining vision (Travis G H, et al. Diseases caused by defects in the visual cycle: retinoids as potential therapeutic agents. Annu Rev Pharmacol Toxicol 2007; 47:469-512). Defects in 11-cis-retinal production are associated with a number of inherited degenerative retinopathies (Gu S M, et al. Mutations in RPE65 cause autosomal recessive childhood-onset severe retina dystrophy. Nature genetics 1997; 17:194-197). Two examples are Leber congenital amaurosis (LCA), a childhood-onset retinal disease causing severe visual impairment; and retinitis pigmentosa (RP), another retinopathy with a more variable age of onset.

LCA is an inherited, severe, and currently incurable retinal degeneration that is a leading cause of blindness during childhood. At or soon after birth, LCA patients characteristically exhibit severe visual impairment evidenced by wandering nystagmus, amaurotic pupils, a pigmentary retinopathy with loss of cone and rod sensitivity, absent or greatly attenuated electroretinogram (ERG) responses and a ˜100 folds decrease in cone flicker amplitude (Perrault I, et al. Leber congenital amaurosis. Mol Genet Metab 1999; 68:200-208; Fazzi E, et al. Leber's congenital amaurosis: an update. Eur J Paediatr Neurol 2003; 7:13-22; Fazzi E, et al. Response to pain in a group of healthy term newborns: behavioral and physiological aspects. Functional neurology 1996; 11:35-43).

RPE65, a 65 kDa protein specific to and abundant in the RPE that catalyses the isomerization of fatty acid all-trans-retinyl esters to 11-cis-retinol, is generally considered as the retinoid isomerase involved in the regeneration of 11-cis-retinal (Hamel C P, et al. Molecular cloning and expression of RPE65, a novel retinal pigment epithelium-specific microsomal protein that is post-transcriptionally regulated in vitro. J Biol Chem 1993; 268:15751-15757; Jin M, et al. Rpe65 is the retinoid isomerase in bovine retinal pigment epithelium. Cell 2005; 122:449-459; Moiseyev G, et al. RPE65 is the isomerohydrolase in the retinoid visual cycle. Proceedings of the National Academy of Sciences of the United States of America 2005; 102:12413-12418; Redmond T M, et al. Mutation of key residues of RPE65 abolishes its enzymatic role as isomerohydrolase in the visual cycle. Proceedings of the National Academy of Sciences of the United States of America 2005; 102:13658-13663). Mutations in the RPE65 gene account for up to 16% of LCA cases and 2% of autosomal recessive RP cases (Gu S M, supra; Marlhens F, et al. Mutations in RPE65 cause Leber's congenital amaurosis. Nature genetics 1997; 17:139-141; Morimura H, et al. Mutations in the RPE65 gene in patients with autosomal recessive retinitis pigmentosa or leber congenital amaurosis Proceedings of the National Academy of Sciences of the United States of America 1998; 95:3088-3093; Thompson D A, et al. Genetics and phenotypes of RPE65 mutations in inherited retinal degeneration, Investigative ophthalmology & visual science 2000; 41:4293-4299; Lorenz B, et al. Early-onset severe rod-cone dystrophy in young children with RPE65 mutations. Investigative ophthalmology & visual science 2000; 41:2735-2742). Spontaneous or engineered deletions of Rpe65 in mice and dogs result in 11-cis-retinal deficiency, an early-onset and slowly progressive retinal degeneration with dramatically reduced electroretinogram (ERG) responses and typical LCA pathology accompanied by accumulation of fatty acid all-trans-retinyl esters in the RPE (Redmond T M, et al. Rpe65 is necessary for production of 11-cis-vitamin A in the retinal visual cycle. Nature genetics 1998; 20:344-351; Pang J J et al. Retinal degeneration 12 (rd12): a new, spontaneously arising mouse model for human Leber congenital amaurosis (LCA). Molecular vision 2005; 11:152-162; Wrigstad A, et al. Ultrastructural changes of the retina and the retinal pigment epithelium in Briard dogs with hereditary congenital night blindness and partial day blindness. Experimental eye research 1992; 55:805-818; Acland G M, et al. Gene therapy restores vision in a canine model of childhood blindness. Nature genetics 2001; 28:92-95; Imanishi Y, et al. Noninvasive two-photon imaging reveals retinyl ester storage structures in the eye. The Journal of cell biology 2004; 164:373-383).

Several possible therapies for treating LCA are being investigated. RPE65 gene augmentation therapy and retinal prostheses have shown preliminary encouraging signs of visual rescue in early-stage clinical evaluations (Bainbridge J W, et al. Effect of gene therapy on visual function in Leber's congenital amaurosis. The New England journal of medicine 2008; 358:2231-2239; Maguire A M, et al. Safety and efficacy of gene transfer for Leber's congenital amaurosis. The New England journal of medicine 2008; 358:2240-2248; Yanai D, et al. Visual performance using a retinal prosthesis in three subjects with retinitis pigmentosa. American journal of ophthalmology 2007; 143:820-827).

Recently, visual chromophore replacement therapy with 9-cis-retinal has been proposed as a novel pharmacological approach to bypass the defective retinoid cycle (Van Hooser J P, et al. Rapid restoration of visual pigment and function with oral retinoid in a mouse model of childhood blindness. Proceedings of the National Academy of Sciences of the United States of America 2000; 97:8623-8628; Van Hooser J P, et al. Recovery of visual functions in a mouse model of Leber congenital amaurosis. J Biol Chem 2002; 277:19173-19182; Alerman T S, et al. Impairment of the transient pupillary light reflex in Rpe65(−/−) mice and humans with leber congenital amaurosis. Investigative ophthalmology & visual science 2004; 45:1259-1271; Batten M L, et al. Pharmacological and rAAV Gene Therapy Rescue of Visual Functions in a Blind Mouse Model of Leber Congenital Amaurosis. PLoS Med 2005; 2:e333). 9-cis-retinal binds to opsin to form the rod cell pigment, iso-rhodopsin, which initiates phototransduction similarly to rhodopsin. It has been shown that oral administration of 9-cis-retinal or its precursors have regenerated opsin as iso-rhodopsin in the eyes, improved retinal function as assessed by ERG responses, and ameliorated the pupillary light reflex in Rpe65 and Lrat knockout mice, which are two genetic models of LCA. There is a need to further develop synthetic 9-cis-retinoids in orally-, gastric-, locally- (such as intravitreal), or intravenously-administered formulations for the treatment of various forms of inherited retinal degeneration caused by defects in the retinoid cycle.

BRIEF SUMMARY

Pharmaceutical formulations comprising artificial retinoids in a lipid vehicle are described. The artificial retinoids can be used to bypass critical blockades in the retinoid cycle, such as RPE65 deficiency or mutation, thereby generating an artificial cis-retinoid chromophore that can functionally combine with opsin. Also described are dosage formulations of the pharmaceutical formulations, including single, intermittent and daily dosing regimens.

Thus, one embodiment provides a pharmaceutical formulation comprising a lipid vehicle and one or more 9-cis-retinyl esters of Formula (I)

wherein R is an alkyl group or an alkenyl group; and the lipid vehicle comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

In a particular embodiment, the 9-cis-retinyl ester of Formula (I) is 9-cis-retinyl acetate.

In a particular embodiment, the lipid vehicle comprises soybean oil.

A further embodiment provides a dosage formulation suitable for daily dosing of a 9-cis-retinyl ester to a subject in need thereof, the dosage formulation comprising about 1.25-20 mg/mL of 9-cis-retinyl acetate in soybean oil, wherein the dosage formulation provides about 1.25-40 mg/m² of the 9-retinyl acetate by body surface area of the subject over a 24-hour period.

Another embodiment provides a dosage formulation suitable for a single dosing by intravitreal administration of 9-cis-retinyl acetate to a subject, the dosage formulation comprising about 18-40% mg/mL of 9-cis-retinyl acetate in soybean oil.

A further embodiment provides a method of treating Leber congenital amaurosis in a human subject, comprising: administering a pharmaceutical formulation having an effective amount of one or more 9-cis-retinyl esters of Formula (I) in a lipid vehicle, the lipid vehicle comprising more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

In a particular embodiment, the 9-cis-retinyl ester of Formula (I) employed in the method is 9-cis-retinyl acetate.

In a particular embodiment, the lipid vehicle employed in the method comprises soybean oil.

A further embodiment provides a method comprising administering, to a human subject deficient in 11-cis-retinal, a pharmaceutical formulation having an effective amount of one or more 9-cis-retinyl esters of Formula (I) in a lipid vehicle, the lipid vehicle comprising more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

In a particular embodiment, the 9-cis-retinyl ester of Formula (I) employed in the method is 9-cis-retinyl acetate.

In a particular embodiment, the lipid vehicle employed in the method comprises soybean oil.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 (A-D) shows the relative absorptions of 9-cis-retinyl acetate in soybean oil and plasma retention of its active metabolites, including fatty acid 9-cis-retinyl esters and 9-cis-retinol.

FIG. 2 (A-C) shows a dose-dependent increase in both a-wave and b-wave amplitudes in mice treated with a single dose of 9-cis-retinyl acetate in soybean oil.

FIG. 3 shows a dosing regimen during a 14-day period in which single-flash ERGs were recorded and retinoid levels in the eyes were measured.

FIG. 4 (A-D) shows ERGs in a dose-dependent increase in the amplitudes of both a- and b-waves in treated as compared to baseline 5-week-old Rpe65^(−/−) mice.

FIG. 5 shows a dosing regimen and evaluation of ERGs and retinoid analyses after three daily doses 9-cis-retinyl acetate in soybean oil.

FIG. 6 (A-F) shows dose-dependent a- and b-wave amplitudes of ERG responses recorded up to day 9 after three daily doses of 9-cis-retinyl acetate in soybean oil.

FIG. 7 shows an intermittent dosing regimen and a daily dosing regimen during an 8-week period.

FIG. 8 (A-D) shows a dose-dependent increase in the amplitude of a- and b-waves on days 28 and 56 in the intermittent dosing regimen and daily dosing regimen.

FIG. 9 (A-I) shows, following a long term administration of 9-cis-retinyl acetate, a dose-dependent protective effect on the retina as assessed by the lengths of the photoreceptor outer segments.

FIG. 10 shows the plasma levels of retinoids as determined by HPLC after 9-cis-retinyl acetate administration.

FIG. 11 (A-D) shows the retinoids in the eyes and liver after 14-day daily treatment with 9-cis-retinyl acetate.

FIG. 12 shows the kinetics of 9-cis-retinal disappearance from the eye after 3 daily doses of 9-cis-retinyl acetate.

FIG. 13 (A-B) shows the retinoid content in the eyes of Rpe65−/− mice after intermittent and daily treated with 9-cis-R-Ac for 8 weeks.

FIG. 14 (A-C) shows the retinoid analyses in livers of Rpe65−/− mice after 56-day intermittent and daily treatment with 9-cis-retinyl acetate.

DETAILED DESCRIPTION OF THE INVENTION

Pharmaceutical formulations of 9-cis-retinyl esters suitable for retinoid replacement therapy are described. More specifically, the pharmaceutical formulation comprises one or more 9-cis-retinyl esters and a lipid vehicle.

As used herein, “retinoids” refers to a class of chemical compounds, natural or artificial, related to vitamin A. Structurally, retinoids share a common core structure composed of a cyclic end group, a conjugated polyene side chain and a polar end group. Naturally occurring retinoids include, for example, vitamin A (11-trans-retinol), 11-trans-retinal, and 11-trans-retinoic acid. Artificial or synthetic retinoids suitable for retinoid replacement therapy include, for example, 9-cis-retinyl esters, as defined herein, 9-cis-retinal and 9-cis-retinol.

As discussed herein, 9-cis-retinyl esters can act as precursors of a prodrug form or a prodrug of 9-cis-retinal, which is capable of functionally combining with opsins, thus completing the retinoid cycle despite, for example, RPE65 deficiency or mutation.

Thus, one embodiment describes a pharmaceutical formulation comprising: one or more 9-cis-retinyl esters and a lipid vehicle, the one or more 9-cis-retinyl esters being suspended in a lipid vehicle.

9-Cis-Retinyl Esters

9-cis-retinyl esters refer to the following generic structure of Formula (I):

wherein R is an alkyl group or an alkenyl group.

“Alkyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, having up to twenty two carbon atoms. In certain embodiments, an alkyl may comprise twelve to seventeen carbon atoms (also referred to as “C₁₂₋₁₇ alkyl”). In certain embodiments, an alkyl may comprise twelve to fifteen carbon atoms (also referred to as “C₁₂₋₁₅ alkyl”). In certain embodiments, an alkyl may comprise one to eight carbon atoms (also referred to as “C₁₋₈ alkyl”). In other embodiments, an alkyl may comprise one to six carbon atoms (also referred to as “C₁₋₆ alkyl”). In further embodiments, an alkyl may comprise one to four carbon atoms (also referred to as “C₁₋₄ alkyl”). The alkyl is attached to the rest of the molecule by a single bond, for example, methyl, ethyl, n-propyl, 1-methylethyl (iso-propyl), n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl), 3-methylhexyl, 2-methylhexyl, and the like. Unless stated otherwise specifically in the specification, an alkyl group may be optionally substituted by one or more of the following substituents: halo (including —F, —Br, —Cl and —I), cyano (—CN), nitro (—NO₂), oxo (═O), and hydroxyl (—OH).

“Alkenyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing at least one unsaturation (i.e., C═C), having from two to up to twenty carbon atoms. In various embodiments, R is C₁₂₋₁₇ alkenyl, C₁₋₈ alkenyl, C₁₋₆ alkenyl or C₁₋₄ alkenyl. Unless stated otherwise specifically in the specification, an alkyl group may be optionally substituted by one or more of the following substituents: halo (including —F, —Br, —Cl and —I), cyano (—CN), nitro (—NO₂), oxo (═O), and hydroxyl (—OH).

In certain embodiments, the 9-cis-retinyl esters are artificial retinoids that act as precursors (i.e., pre-drugs) of a pro-drug form of 9-cis-retinal. More specifically, the 9-cis-retinyl esters can be converted by the liver to a metabolic pro-drug form, namely fatty acid 9-cis-retinyl esters, which are stored in the liver in hepatic lipid droplets. Fatty acid 9-cis-retinyl esters and retinol are mobilized from the liver and enter the circulation where they travel to the eye and RPE. There, they are converted to 9-cis-retinal which ultimately combines with photoreceptor opsins to form active visual pigments.

A preferred 9-cis-retinyl ester is 9-cis-retinyl acetate (i.e., R is methyl). Also referred to as “9-cis-R-Ac”, 9-cis-retinyl acetate is a pharmaceutical pre-drug, which is metabolized by the liver to fatty acid 9-cis-retinyl esters, such as 9-cis-retinyl palmitate. Fatty acid 9-cis-retinyl esters and retinol are then converted to 9-cis-retinal in the eye and RPE as replacement of deficient chromophores such as 11-cis-retinal.

9-cis-R-Ac can be prepared by initially converting all-trans-retinyl acetate (Sigma-Aldrich) to a mixture of 9-cis-retinyl acetate and all-trans-retinyl acetate in the presence of a palladium catalyst (e.g., palladium salts, palladium oxides). The mixture of 9-cis-retinyl acetate and all-trans-retinyl acetate are then hydrolyzed to produce a mixture of 9-cis-retinol and all-trans-retinol. The pure 9-cis-retinol can be isolated by selective recrystallization and further esterified to pure 9-cis-R-Ac. A detailed description of the processes for preparing and purifying 9-cis-R-Ac can be found, for example, in GB Patent No. 1452012.

In other embodiments, the retinyl esters are pro-drugs (rather than precursors of pro-drugs) and can be directly converted to 9-cis-retinal in the eye and RPE. The pro-drug forms of the 9-cis-retinyl esters are typically fatty acid 9-cis-retinyl esters, in which R is a C₁₁₋₂₁ alkyl. As used herein, “fatty acid” refers to a carboxylic acid having a long aliphatic chain, which can be saturated (alkyl) or unsaturated (alkenyl). Typically, the aliphatic chain contains at least 11 carbons and can be as long as 21 carbons. Exemplary fatty acids include, without limitation, lauric acid, palmitic acid, palmitoleic acid, oleic acid, linoleic acid, and linolenic acid.

Thus, in one embodiment, R is a C₁₅ alkyl, and the 9-cis-retinyl ester of Formula (I) is 9-cis-retinyl palmitate.

In a further embodiment, R is a C₁₇ alkyl, and the 9-cis-retinyl ester of Formula (I) is 9-cis-retinyl stearate.

In other embodiment, R is a C₁₇ alkenyl, and the 9-cis-retinyl ester of Formula (I) is 9-cis-retinyl oleate.

The 9-cis-retinyl esters described herein can be prepared from 9-cis-retinol using appropriate esterifying agents in a manner similar to the preparation of 9-cis-R-Ac, the methods of which are within the knowledge of one skilled in the art.

As demonstrated herein, low doses (1 and 4 mg/kg) of an exemplary pre-drug 9-cis-R-Ac were found to be clinically safe and effective in maintaining visual function in Rpe65^(−/−) mice as assessed by ERG recordings, retinoid levels in the eyes, retinal histology and vision-dependent behavioral studies. This compound is useful in treating, for example, humans with retinopathies stemming from inadequate retinoid chromophore generation.

Lipid Vehicles

Typically, the 9-cis-retinyl esters are oily substances and are lipophilic. Thus, the pharmaceutical formulation described may further comprise a lipid vehicle.

Because 9-cis-retinyl esters are light and oxygen-sensitive, their stability is critical to the efficacy and shelf-life of the formulation. A suitable lipid vehicle is therefore selected based on its ability to stabilize the 9-cis-retinyl esters suspended or solubilized therein.

As used herein, “lipid” or “lipid vehicle” refers to one or a blend of fatty acid esters. In various embodiments, the lipid vehicle comprises one or more triglycerides, which are formed when a single glycerol is esterified by three fatty acids. Triglycerides include both vegetable oils and animal fats.

In the context of describing the lipid vehicles, triglycerides are often simply referred to by their corresponding fatty acids. The fatty acids of the triglycerides can be saturated, monounsaturated and polyunsaturated, depending on the number of carbon-carbon double bond (C═C) in the aliphatic chains. A saturated fatty acid contains no carbon-carbon double bond in the aliphatic chain. Examples of saturated fatty acids include, e.g., palmitic and stearic acids. A monounsaturated fatty add contains a single carbon-carbon double bond (C═C) in the aliphatic chain. Examples of monounsaturated fatty acids include, e.g., oleic and palmitoleic acids. A polyunsaturated fatty acid contains at least two carbon-carbon double bonds in the aliphatic chain. Examples of polyunsaturated fatty acids include, e.g., linoleic acid (two C═C) and linolenic acid (three C═C). Further, the polyunsaturated fatty acids include omega-3 fatty acids and omega-6 fatty acids, depending on the location of the final C═C bond in the aliphatic chain. For example, linoleic is an omega-6 fatty acid, whereas linolenic is an omega-3 fatty acid.

Typically, the lipid vehicle is a blend of fatty acids, the relative amounts of each can impact the overall characteristics of the lipid vehicle, especially its ability to resist oxidation and to stabilize the 9-cis-retinyl ester suspended therein.

In certain embodiments, the lipid vehicle comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15. In specific embodiments, the lipid vehicle comprises triglyceride linoleate and triglyceride linolenate in a ratio (by weight) of less than 15, which collectively are more than 50% of the total weight of the lipid vehicle.

In other embodiments, the lipid vehicle can be a vegetable-based oil or oil blend that comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

Table 1 shows a number of vegetable oils and their fatty acid components in percentage weight (see, e.g., U.S. Published Application No. 2007071872).

TABLE 1 MUFA PUFA Lipid Source SAFA ω7 + ω9 ω6 ω3 ω6:ω3 Total Sunflower 13 27 61 0.1 610 101.1 Peanut 14 43 35 0.1 350 92.1 Grapeseed 14 21 68 0.5 136 103.5 Corn 16 32 51 1 51 100 Palm 51 40 9 0.25 36 100.25 Olive (1) 16 70 13 0.6 22 100.6 Coconut 92 7 1.5 0.1 15 100.6 Olive (2) 15 79 5 0.6 8 99.6 Wheat germ 20 18 55 7 8 100 Soybean 16 22 54 7.5 7 99.5 Walnut 11 15 62 12 5 100 Canola 7 63 20 10 2 100 Chia 9.7 6.7 19 64 0.3 99.4 Flax 6.9 19.5 15 57.5 0.26 98.9 Perilla 8.5 14.4 12.6 63.2 0.20 98.7 SAFA = Saturated fatty acids MUFA = Monosaturated fatty acids PUFA = Polyunsaturated fatty acids ω6:ω3 = ratio of omega-6 to omega-3 polyunsaturated fatty acids.

Soybean oil is a suitable lipid vehicle as it comprises about 62% of polyunsaturated fatty acid (54% linoleic and 8% linolenic), 25% monounsaturated fatty acid (oleic), and 16% saturated fatty acid (11% palmitic acid, and 5% stearic acid).

Soybean oil is a clear and odorless oil that is miscible with the 9-cis-retinyl esters described herein. When compared to fatty acids containing lower concentration of polyunsaturated fatty acids (e.g., Canola oil and olive oil, which contains about 30% and less than 20% polyunsaturated fatty acids, respectively), soybean oil unexpectedly exhibits superior stabilizing effect, as evidenced by the higher contents of pure 9-cis-retinyl acetate retained in the formulations following a two-week period.

In addition, when compared to fatty acids that have a higher ratio of omega-6 to omega-3 polyunsaturated fatty acid, soybean oil also exhibits superior stabilizing effect. For example, sunflower oil, although having a total amount of polyunsaturated fatty acids (61%) comparable to that of soybean oil, has a much higher ratio of omega-6 to omega-3 polyunsaturated fatty acid (over 600) than soybean oil (about 7). As shown in Table 2 (Example 1), the stabilizing effect of sunflower oil is comparable to that of Canola oil, both are much lower than soybean oil (USP grade).

Significantly, the soybean oil formulations are most stable as compared to formulations of other vehicles at temperatures close to physiological conditions (e.g., 40° C.). Highly refined soybean oil that meets the U.S.P. monograph is preferred (e.g., as provided by Spectrum Chemicals) as it was observed that U.S.P. grade soybean oil provides enhanced stabilization than commercial grade soybean oil (see, Example 1).

Furthermore, the soybean oil vehicle provides the highest plasma level of the metabolites of 9-cis-retinyl esters. FIG. 1 shows the relative absorptions of 9-cis-R-Ac and plasma retention of its active metabolites, fatty acid 9-cis-retinyl esters and 9-cis-retinol.

It is thus demonstrated that soybean oil confers both stability of 9-cis-retinyl esters and high plasma retention of the active metabolites of the same, thereby providing synergistic benefits to the formulations.

In a further embodiment, the lipid vehicle is walnut oil, which comprises 72% polyunsaturated fatty acids (62% linoleic and 12% linolenic).

In yet another embodiment, the lipid vehicle is wheat germ oil, which comprises 62% polyunsaturated fatty acids (55% linoleic and 7% linolenic).

Formulations

In general, the pharmaceutical formulations can include any of the 9-cis-retinyl ester described herein combined with a suitable lipid vehicle.

One embodiment describes a pharmaceutical formulation comprising one or more 9-cis-retinyl esters in a lipid vehicle, wherein the lipid vehicle comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

A further embodiment describes a pharmaceutical formulation comprising 9-cis-retinyl acetate in a lipid vehicle, wherein the lipid vehicle comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

A further embodiment describes a pharmaceutical formulation comprising 9-cis-retinyl acetate in a lipid vehicle, wherein the lipid vehicle comprises triglyceride linoleate and triglyceride linolenate in a ratio (by weight) of less than 15, which collectively are more than 50% of the total weight of the lipid vehicle.

A further embodiment describes a pharmaceutical formulation comprising 9-cis-retinyl acetate in soybean oil.

Yet another embodiment describes a pharmaceutical formulation comprising 9-cis-retinyl acetate in walnut oil.

Yet another embodiment describes a pharmaceutical formulation comprising 9-cis-retinyl acetate in wheat germ oil.

In various embodiments, the pharmaceutical formulation comprises up to 40% (by weight) 9-cis-retinyl esters, up to 30% (by weight) 9-cis-retinyl esters, up to 25% (by weight) 9-cis-retinyl esters, up to 10% (by weight) 9-cis-retinyl esters, up to 5% (by weight) 9-cis-retinyl esters.

Optional Components

The pharmaceutical formulations described herein can optionally comprise additional components which enhance stability and palatability. For example, one or more stabilizer (e.g., an anti-oxidant) may be included to impart further stabilizing effect. Further, flavoring agents may be added to orally-administered formulations to improve the taste.

The anti-oxidant employed in the present disclosure may be one or more of the following: α-tocopherol, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ascorbyl palmitate and propyl gallate, tert-butyl hydroquinone (TBHQ), Chelating agents such as disodium edetate and calcium disodium edentate may be employed.

Flavoring agents and flavor enhancers make the pharmaceutical formulations more palatable to the patient. Common flavoring agents and flavor enhancers for pharmaceutical products that may be included in the composition of the present invention include maltol, vanillin, ethyl vanillin, menthol, citric acid, fumaric acid, ethyl maltol, and tartaric acid. Flavored oils (e.g., lemon oil) are preferred as they are miscible with the lipid vehicle. Sweetening agents such as sorbitol, saccharin, sodium saccharin, sucrose, aspartame, fructose, mannitol and invert sugar may be added to improve the taste.

Water, surfactants or emulsifiers can be added to the oil-based formulations to form a mixture suitable for oral administration (e.g., in the form of a beverage) or intravenous injection. Suitable surfactants and emulsifiers include, for example, soy lecithin and dipalmitoylphosphatidyl choline. Beverages, such as soy milk, can also be added directly to the formulations described herein.

Thus, one embodiment provides a beverage comprising one or more 9-cis-retinyl esters and a lipid vehicle, wherein the lipid vehicle comprises more than 50 w/w % polyunsaturated fatty acids, the polyunsaturated fatty acids including an omega-6 fatty acid and an omega-3 fatty acid in a ratio (by weight) of less than 15.

A further embodiment provides a drinkable formula, emulsion or beverage comprising 9-cis-retinyl acetate, soybean oil and a drinkable liquid medium. In certain embodiments, the drinkable liquid medium is in the form of oil-in-water emulsion (e.g., milk or soy milk). Additional emulsifiers, such as acacia, tragacanth gums, and methyl cellulose, can also be employed.

A further embodiment provides an oral formulation in the form of capsules, the capsules containing 9-cis-retinyl acetate, soybean oil. Additional excipients such as anti-oxidants can be included, as is recognized by one skilled in the art.

Administration and Dosage Formulations

The pharmaceutical formulation described herein can be administered to a subject by oral, gastric or local administration such as intravitreal injection and intravenous injection.

Oral administration can be effected by oral gavage, or via a drinkable formula or beverage which includes one or more 9-cis-retinyl esters, a lipid vehicle and a beverage such as soymilk.

Gastric administration can be effected by gastric gavage (e.g., stomach tube).

Local administration such as intravitreal (through the eye) injection and intravenous injection are carried out with syringes.

As used herein, a “subject” refers to a patient, may be from any mammalian species, e.g. primates, particularly humans; rodents, including mice, rats, and hamsters; rabbits; equines; bovines; canines; felines; etc. Animal models, in particular, genetically manipulated animals, are of interest for experimental investigations, providing a model for treatment of human diseases, e.g., LCA.

Typically, all doses of 9-cis-R-Ac are completely miscible in the lipid vehicles, including soybean oil, USP (Spectrum Chemicals). In various embodiments, single, intermittent and daily administrations are described. Further, based on the post-absorptive levels of their pharmacologically active metabolites in plasma, the dosage and corresponding efficacy of the 9-cis-retinyl esters can be assessed by using ERG, visual acuity, full-field stimulus testing, visual field analysis, color vision testing.

As shown in the Examples, a dose-dependent improvement of both the level and duration of retinal function were observed in Rpe65 and Lrat knockout mice, which are two genetic models of LCA. Importantly, pharmacological activity was sustained for sufficiently long periods after dosing to enable formulation of a flexible, intermittent dosing schedule.

More specifically, single doses of 9-cis-R-Ac (6.25-50 mg/kg) led to significant dose-dependent improvement of ERG responses. Daily doses (1, 4 and 12.5 mg/kg) for two weeks were well tolerated and induced remarkable improvement of retinal function. Significant dose-dependent improvements of ERG responses were observed 6 days after administration of 9-cis-R-AC daily for 3 days at 1, 4 and 12.5 mg/kg. Mice given either daily or intermittent 9-cis-R-Ac treatment at 1 and 4 mg/kg/day and evaluated two months later displayed dose-dependent improvement of retinal function and morphology 8 weeks later whereas retinal function deteriorated in comparable 3-month-old control animals.

Thus, in one embodiment, described herein is a dosage formulation suitable for 24 hour or daily dosing of a 9-cis-R-Ac to a subject in need thereof comprising about 1.25-20 mg/mL 9-cis-R-Ac in soybean oil, wherein the dosage formulation provides about 1.25-40 mg/m² of the 9-cis-R-Ac by body surface area of the subject over a 24-hour period.

In another embodiment, the dosage formulation provides a time to maximum or peak plasma concentration of 9-cis-retinyl esters at about 3-6 hours following oral or gastric administration of the dosage formulation. As used herein, “peak plasma concentration” is a pharmacokinetic measure for assessing bioavailability of a pharmaceutical product. Plasma drug concentration increases with extent of absorption; the peak is reached when drug elimination rate equals absorption rate. In addition to the maximum (peak) plasma drug concentration, the corresponding peak time (when maximum plasma drug concentration occurs), and area under the plasma concentration-time curve are also parameters of pharmacokinetics.

In a further embodiment, described herein is a dosage formulation suitable for a single dosing by intravitreal administration of 9-cis-retinyl acetate to a subject, the dosage formulation comprising about 18-40% mg/mL of 9-cis-retinyl acetate in soybean oil. It has been found that a single dosage for intravitreal administration can last for days, even weeks in the subject's eye, possibly through a manner of sustained release.

Use of 9-Cis-Retinyl Esters as Retinoid Replacement Therapies

Also described herein are methods of using 9-cis-retinyl esters of Formula (I) as retinoid replacement therapies for retinal degeneration in humans.

Appropriate animal models for evaluating the efficacy and safety of the 9-cis-retinyl esters as retinoid replacement therapies were carried out (see, Examples). The animal models used are Rpe65^(−/−) mice, which lack retinal pigmented epithelium-specific 65 kDa protein (RPE65) and develop retinopathy and blindness resembling LCA in humans.

The pharmacokinetic and pharmacodynamic effects of the pre-drug indicate that the pre-drug is converted to a pro-drug in the liver, i.e. to mostly 9-cis-retinyl palmitate, in the Rpe65^(−/−) mouse model (see, Examples). Further, in the in the Rpe65^(−/−) mouse model, 9-cis-retinoids were observed to have been delivered to the retina in two ways, i.e. primarily and promptly from the circulating blood and secondarily and more slowly from 9-cis-retinoids stored in the liver (see, Example 5).

By using several different regimens in Rpe65^(−/−) mice to evaluate drug efficacy and safety, it is demonstrated that 9-cis-retinyl esters can be used as synthetic retinoids to treat human LCA patients. Both dose- and administration period-dependent retention of visual function were observed, even at the lowest 1 and 4 mg/kg doses tested (FIGS. 2, 4, 6, 8). Significantly, a dose-dependent prolongation of efficacy was observed for the pre-drug 9-cis-R-Ac.

Thus, one embodiment provides a method of treating Leber congenital amaurosis in a human subject, comprising administering a pharmaceutical formulation having an effective amount of one or more 9-cis-retinyl esters of Formula (I) in soybean oil. In a more specific embodiment, the 9-cis-retinyl esters of Formula (I) is 9-cis-retinyl acetate.

A further embodiment provides a method comprising: administering, to a human subject deficient in 11-cis-retinal, a pharmaceutical formulation having an effective amount of one or more 9-cis-retinyl esters of Formula (I) in soybean oil In a more specific embodiment, the 9-cis-retinyl esters of Formula (I) is 9-cis-retinyl acetate.

The various embodiments described herein are further illustrated by the following non-limiting examples.

EXAMPLES Materials, Methodology and Analysis

Electroretinogram (ERG)—ERGs were recorded on anesthetized mice as described in, e.g., Maeda A, et al. Role of photoreceptor-specific retinol dehydrogenase in the retinoid cycle in vivo. J Biol Chem 2005; 280:18822-18832; and Maeda T, et al. A Critical Role of CaBP4 in the Cone Synapse. Investigative ophthalmology & visual science 2005; 46:4320-4327.

Briefly, mice first were dark-adapted overnight prior to recording. Then under a safety light, mice were anesthetized by intraperitoneal injection of 20 μl/g body weight of 6 mg/ml ketamine and 0.44 mg/ml xylazine diluted with 10 mM sodium phosphate, pH 7.2, containing 100 mM NaCl. Pupils were dilated with 1% tropicamide. A contact lens electrode was placed on the eye and a reference electrode and ground electrode were positioned on the ear and tail, respectively. ERGs were recorded with the universal testing and electrophysiologic system (UTAS) E-3000 (LKC Technologies, Inc.).

Single-flash recording—White light flash stimuli were employed with a range of intensities (from −3.7 to 2.8 log cd·s·m^(·2)), and flash durations were adjusted according to intensity (from 20 μs to 1 ms). Two to five recordings were made at sufficient intervals between flash stimuli (from 10 s to 10 min) to allow mice to recover. Typically, four to eight animals were used for recording each point. The one-way ANOVA test was used for statistical analysis of responses.

Histology and Immunohistochemistry—Histological procedures employed for the eye analyses as described in Maeda A, et al. supra.

Analyses of Retinoic Acid and Non-polar Retinoids—All experimental procedures related to extraction, retinoid derivatization and separation of retinoids were done under dim red light provided by a Kodak No. 1 safelight filter (transmittance>560 nm). Retinoic acid extraction from liver was performed as formerly described in, e.g., Batten M L. et al. supra. Analyses of polar retinoids in plasma, eye and liver were performed with an Agilent 1100 HPLC and two tandem normal phase columns: a Varian Microsorb Silica 3 μm, 4.6×100 mm (Varian, Palo Alto, Calif.) and an Ultrasphere-Si, 5 μm, 4.6×250 mm column (Aleman T S, et al. supra). An isocratic normal phase system of hexane: 2-propanol:glacial acetic acid (1000:4.3:0.0.675; v/v/v) was used for elution at a flow rate of 1 ml/min at 20° C. with detection at 355 nm. Calibration was done with standards of all-trans-retinoic acid and 9-cis-retinoic acid purchased from Sigma-Aldrich. Analyses of non-polar retinoids in plasma, eye and liver were carried out by normal phase HPLC (Ultrasphere-Si, 5 μm, 4.6×250 mm, Beckman, Fullerton, Calif.) with 10% ethyl acetate and 90% hexane at a flow rate of 1.4 ml/min with detection at 325 nm by an HP1100 HPLC with a diode array detector and HP Chemstation A.03.03 software.

Example 1 Stability Tests of Various Formulations

Several different lipid-based formulations of 9-cis-R-Ac were prepared to test the stability conferred by various lipid vehicles. As 9-cis-R-Ac was considered light sensitive, amber vials were used whenever possible and the compound was handled under gold fluorescent light. 9-cis-R-Ac was removed from the −20° C. freezer and warmed to room temperature for 30 minutes. Compound handling was performed under a flow of Argon gas as the compound was transferred into pre-weighed amber vials and re-weighed to calculate the amount of compound before the vials were backfilled with argon and stored at −20° C. until use.

Mixtures of 9-cis-R-Ac (1.4 to 8 mg/mL) in the various carriers/vehicles were prepared using the amber vials containing accurately weighed compound. The sample vials were backfilled with argon and mixed by vortexing. The polyoxyl 35 caster oil samples were heated to 60° C. Each sample was divided into two portions and stored at 4° C. or 40° C. The samples were analyzed by HPLC for 9-cis-retinyl acetate content following preparation (day 0), and at time points up to 2 weeks.

Samples for HPLC analysis were diluted to approximately 0.1 mg/mL in THF. Samples were analyzed immediately or stored at −20° C. or −70° C. for up to 1 week until analysis. Percent recovery was calculated relative to the formulation concentration at day 0 by HPLC.

Unexpectedly, soybean oil (USP), with and without BHT, provides the most stable suspension for 9-cis-R-Ac, particularly at physiological temperature (about 40° C.), as indicated by the percentage amount of the 9-cis-R-Ac content in the formulation at Day 7 and Day 14 (Table 2).

TABLE 2 Stability 4° C. 40° C. Vehicle Day 7 Day 14 Day 7 Day 14 Canola oil 100% 99% 95% 89% Rapeseed oil 102% 102% 95% 88% Sunflower seed oil 99% 99% 91% 87% Clove leaf oil 96% 93% 16% 6% Olive oil 99% 97% 91% 89% Eugenol 95% 90% 6% 2% Soybean oil 107% 101% 93% 69% Soybean oil, USP 103% ± 1% 101% ± 1% 99% ± 2% 98% ± 1% with 0.1% w/v BHT 107% ± 1% 104% ± 1% 103% ± 1%  97% ± 1% with 0.1% w/v alpha tocopherol 104% ± 2% 102% ± 1% 101% ± 1%  94% ± 0% Polyoxyl 35 castor oil 101% ± 1%  98% ± 2% 95% ± 1% 89% ± 2% 25% Polyoxyl 35 castor oil in water 100% ± 1%  98% ± 1% 80% ± 1% 66% ± 1%

Example 2 Plasma Retention of 9-Cis-Retinyl Acetate Metabolites

Several different oil-based preparations were prepared to test the absorption levels of 9-cis-R-Ac in plasma. More specifically, a single 50 mg/kg dose of 9-cis-retinyl acetate (50 mg/kg) suspended in 4 different vehicle oils was administrated by gastric gavage to 5-week-old C57/Bl6 mice and retinoid levels were determined in the plasma thereafter (n=5 for each time point per group).

Solution of 9-cis-R-Ac in either soybean oil or sunflower oil, as compared to canola and rapeseed oils, provided the best absorption of 9-cis-R-Ac as evidenced by the highest plasma levels of fatty acid 9-cis-retinyl esters and 9-cis-retinol, both active metabolites of 9-cis-R-Ac (FIG. 1A, C, 11). The highest plasma levels of these 9-cis-retinoids were noted at −3 h. Plasma levels of all-trans-retinol and fatty acid all-trans-retinyl esters did not differ significantly, either among the test vehicles did or during the 23 h test period, suggesting that cis-retinoids were not converted to all-trans-retinoids (FIG. 1B, D).

FIG. 10 shows the retinoids in plasma as determined by HPLC. Fatty acid retinyl esters detected early in the elution phase (a, b, c) consisted of four peaks of 9-cis (a, c) and two peaks of all-trans (b) isomers. Both 9-cis-retinol (d) and all-trans-retinol (e) eluted later.

Example 3 Effects of Single Doses of 9-Cis-R-Ac on Retinal Function of Rpe65^(−/−) Mice

Single doses (2-50 mg/kg) of 9-cis-R-Ac in soybean oil were administered to 5-week-old Rpr65Rpe65^(−/−) mice to test whether the pre-prodrug 9-cis-R-Ac was capable of delivering artificial chromophore to the eye.

Mice showed no obvious clinical side effects, even after receiving the highest dosing of 50 mg/kg. Following dark-adaption for 3 days post-gavage, scotopic single flash ERGs were recorded and eyes were collected to assess 9-cis-retinal levels.

Scotopic ERGs of the treated mice showed a dose-dependent increase in both a-wave and b-wave amplitudes (FIG. 2A, B); the lowest tested dose that provided significant improvement after high intensity stimuli was 6.25 mg/kg. Similarly, a dose-dependent accumulation of 9-cis-retinal was found in the eyes of treated mice that correlated with improvement in retinal function (FIG. 2C). No fatty acid 9-cis-retinyl esters were detected in any of the analyzed eyes whereas levels of fatty acid all-trans-retinyl esters ranged from ˜1 to 1.6 nmol/eye and did not differ significantly among the four treatment groups. Moreover, fatty acid all-trans-retinyl ester levels were similar to the 1.2 nmol/eye reported for untreated 5-week-old Rpe65^(−/−) mice.

9-cis-retinol (43 pmol/eye) was detected only in the eyes of mice dosed with 50 mg/kg, whereas all-trans-retinol levels, varying from 14 to 22 pmol/eye, did not differ significantly among the four treatment groups. No 11-cis-retinoids were detected in any of the eyes.

Thus, the results suggest that 9-cis-retinal recombine with opsin to form iso-rhodopsin. Importantly, lower doses of 9-cis-R-Ac (2 and 4 mg/kg) induced positive ERG effects even though only trace levels of 9-cis-retinal were detected in the eye (FIG. 2).

Example 4 Effects of 9-Cis-R-Ac Given Daily for 14 Days

The retinal function of Rpe65^(−/−) and C57Bl/6 mice were tested after repeated daily dosing of 9-cis-R-Ac. To test this directly, 5-week-old Rpe65^(−/−) mice were gavaged daily with 9-cis-R-Ac in soybean oil at doses of 1, 4, or 12.5 mg/kg for 14 days. The mice were exposed to an alternating dark and fluorescent light (luminance range of 500-1500 lux) environment during the last 11 days of treatment. Scotopic single-flash ERGs were recorded and retinoid levels in the eyes were measured (FIG. 3).

ERGs showed a dose-dependent increase in the amplitudes of both a- and b-waves in treated as compared to baseline 5-week-old Rpe65^(−/−) mice (FIG. 4A, B). Even the lowest daily test dose of 1 mg/kg evoked a significant improvement in retinal function as compared to the control group.

9-cis-Retinal was readily detected in the eyes of the knockout animals but neither fatty acid 9-cis-retinyl esters nor 9-cis-retinol were present (FIG. 11A-C). However, fatty acid 9-cis-retinyl esters did accumulate in a dose-dependent manner in the livers of both C57Bl/6 and Rpe65^(−/−) mice (FIG. 11D). The presence of 9-cis-retinal in the eyes of these mice suggests improvement in retinal function as observed in single dose studies of Rpe65^(−/−) mice. There also was a corresponding dose-dependent accumulation of 9-cis-retinal in the eyes of treated mice (FIG. 4C). No 9-cis-retinal was detected in eyes of the baseline and 1 mg/kg treated groups whereas 38±4 and 95±14 pmol were measured in the daily 4 and 12.5 mg/kg groups, respectively. Levels of fatty acid 9-cis-retinyl esters were low (1 pmol/eye) in the 4 and 12.5 mg/kg/day groups, and undetectable in eyes from other groups (FIG. 4D). Neither all-trans-retinol nor 9-cis-retinol was found in any group. Levels of fatty acid all-trans-retinyl esters (essentially palmitate, stearate and oleate) in the eyes of mice exposed to 9-cis-R-Ac ranged from 1.2 to 1.4 nmol/eye, and were not significantly different from those in control eyes (1.2 nmol/eye at 5-weeks of age).

The ERG responses indicated improved efficacy and kinetics of 9-cis-R-Ac in a dose-dependent manner. The lowest dose (1 mg/kg) significantly improved ERG responses as compared with baseline 5-week-old Rpe65^(−/−) mice even though 9-cis-retinal and fatty acid 9-cis-retinyl esters were not detected in the eye (FIG. 4). This suggests that 9-cis-retinal disappears with light exposure (8 h light/16 h dark) and that fatty acid 9-cis-retinyl esters are utilized to regenerate iso-rhodopsin instead. Indeed, accumulation of fatty acid 9-cis-retinyl esters was detected in liver samples in a dose-dependent manner, which suggests that hepatic stores of fatty acid 9-cis-retinyl esters can serve as a reservoir to generate 9-cis-retinal and iso-rhodopsin in the eye.

The daily dosages of 1, 4, 12.5 and 50 mg/kg were all well tolerated by both 5-week-old C57Bl/6 and Rpe65^(−/−) mice in this 14-day study, signifying the safety of the 9-cis-R-Ac.

Example 5 Duration of Improved Retinal Function after 3 Daily Doses of 9-Cis-R-Ac

9-cis-Retinol in the form of fatty acid 9-cis-retinyl esters accumulated in the liver of Rpe65^(−/−) mice given repeated doses of 9-cis-R-Ac of at least 12.5 mg/kg for 2 weeks (see, FIG. 11D, Example 4).

To assess the capability of mice to store 9-cis-retinoids and later utilize them in the retinoid cycle, 9-cis-R-Ac in soybean oil was gavaged once daily for three consecutive days at a dose of 1, 4, or 12.5 mg/kg/day into 5-week-old Rpe65^(−/−) mice kept in the dark. Mice then were exposed to cycles of 8 h of fluorescent light with luminance range of 500-1500 lux followed by 16 h in the dark.

ERGs and retinoid analyses were performed at the end of the first (day 4), second (day 5), fourth (day 7), and sixth (day 9) days of light exposure (FIG. 5). Both a- and b-wave amplitudes of ERG responses recorded up to day 9 (FIG. 6A-F) were dose-dependent at each time point and declined with the number of light exposures. The highest tested dose (12.5 mg/kg/day) significantly improved both a- and b-waves up to day 9 (FIG. 6A-B) at high intensity stimuli, whereas doses of 4 mg/kg and 1 mg/kg showed improvement in a-wave amplitudes up to day 9 and day 7, respectively, and in b-wave amplitudes up to day 9 (FIG. 6C-F). Levels of 9-cis-retinal in the eye also were dose-dependent and decreased over time (FIG. 12). This compound was detected in the retinas of all treated mice at day 4 (FIG. 12), but only in the retinas of mice exposed to 4 and 12.5 mg/kg at day 5, and only in the 12.5 mg/kg group at day 7. No 9-cis-retinal was found in the retinas of treated or control mice by day 9. Thus, daily administration of 9-cis-R-Ac was not needed to deliver 9cis-R-Ac to the eye and sustain improvement in retinal function of Rpe65^(−/−) mice.

Thus, it is shown that the ERG amplitudes improved in a generally dose-dependent manner and this positive effect was maintained for up to 4-6 days after treatment. Moreover, a similar pattern was noted for 9-cis-retinal levels found in the eyes of these animals. Importantly, improvement of ERG responses at the 4 mg/kg dose level lasted for 4-6 days after cessation of treatment when 9-cis-retinal could no longer be found in the eyes. These results indicate that the positive effects of 9-cis-R-Ac therapy are retained by trace levels of 9-cis-retinal in the retina that stabilize the ROS, whereas ERG responses in the control groups had deteriorated. The kinetics of retinoid levels in eyes then were examined during dark-adaptation after light exposure. Importantly, restoration of fatty add 9-cis-retinyl esters and 9-cis-retinal in the eyes occurred during dark-adaptation.

Example 6 Retinal Function of Rpe65^(−/−) Mice after Intermittent and Daily Administration of 9-Cis-R-Ac for 8 Weeks

Because 3 low daily doses of 9-cis-R-Ac improved ERG responses after 6 days of light exposure (FIG. 6A-F), a prolonged 8-week intermittent dosing regimen was carried out.

Rpe65^(−/−) mice were split into two groups (an intermittent group and a daily group), each treated for a total of 8 weeks with 1 or 4 mg/kg of 9-cis-R-Ac. The intermittent group was dosed daily for 3 days followed by a 4-day drug holiday during each week of the 8-week regimen. The daily group was dosed daily for the entire 8-week period. The dosing regimens are illustrated in FIG. 7. Mice were exposed to a daily cycle of 8 h of fluorescent light with luminance range of 500-1500 lux followed by 16 h darkness. ERGs were recorded at day 28 and again at day 56, after which tissues were collected for retinoid analyses of the eye and liver and histology of the eye.

ERG responses of treated mice in intermittent group and daily group were significantly better than those of controls at both day 28 and day 56, and mild tapering of amplitudes between day 28 and day 56 was noted in both the 9-cis-R-Ac treated mice and control mice. Both the intermittent dosing and daily dosing regimens evoked a dose-dependent increase in the amplitude of a- and b-waves on days 28 and 56 (FIG. 8A-D). Responses were more pronounced in the daily dosed than in the intermittently dosed group. The lower dose (1 mg/kg) was sufficient to cause a significant improvement in ERG responses over the control group at high intensity stimuli, irrespective of the treatment schedule. In addition, the amplitudes of the a- and b-waves were similar at day 28 and 56, suggesting that equilibrium may have been achieved between the intake and storage of 9-cis-retinol on one hand and its mobilization in the retina to support the retinoid cycle on the other. In agreement with these ERG results, 9-cis-retinal was detected in a dose-dependent manner in the eyes where levels were higher in mice dosed daily (FIG. 13A). Fatty acid 9-cis-retinyl esters at low variable levels also were found in the eyes of both sets of treated animals (FIG. 13B). A dose-dependent slight increase in fatty acid all-trans-retinyl esters also was noted in the eyes of treated mice regardless of the regimen. In the liver, 9-cis-retinol was essentially stored in the form of fatty acid 9-cis-retinyl esters in a dose and regimen-dependent manner (FIG. 14A, B). Levels of fatty acid all-trans-retinyl esters were not significantly affected by these regimens, although there may have been a slight increase in mice receiving 4 mg/kg 9-cis-R-Ac. Long term administration of 9-cis-R-Ac had a dose-dependent protective effect on the retina as assessed by the lengths of the photoreceptor outer segments (FIG. 9A, C) and number of nuclei in the outer nuclear layer (FIG. 9B, D). These effects were more pronounced in the superior than inferior retina. More highly magnified images of retinal cross sections showed improvement of rod outer segment (ROS) morphology and fewer oil droplet-like structures in parts of the superior and inferior portions of retinas from mice treated with either the 4 mg/kg daily or 4 mg/kg intermittent regimens (FIG. 8E, F). However, no significant change was observed in retinas of mice receiving the 1 mg/kg 9-cis-R-Ac dose by either schedule (FIG. 9G, H) as compared with retinas of control mice (FIG. 9I).

Importantly, ERG responses of mice treated intermittently with 9-cis-R-Ac evidenced no significant difference between the 1 and 4 mg/kg dose groups at day 56, suggesting that the lower 1 mg/kg dose may have similar efficacy if given continuously. As shown in FIG. 9, morphological improvements of ROS were observed such that ROS lengths were significantly longer in the superior retina of mice treated with 4 mg/kg whereas no significant changes were noted in animals given the 1 mg/kg dose. From these observations, it is strongly suggested that treatment regimens of both 1 and 4 mg/kg maintained retinal function in Rpe65^(−/−) mice without significant clinical toxicity or abnormal retinoid accumulation in the eyes and liver.

All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

The invention claimed is:
 1. A liquid oral pharmaceutical formulation suitable for treating a human subject with an endogenous 11-cis-retinal deficiency consisting essentially of 9-cis-retinyl acetate in soybean oil and an anti-oxidant, wherein the soybean oil is U.S.P. grade soybean oil.
 2. The formulation of claim 1, wherein said formulation is not in the form of a capsule.
 3. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present up to 30% by weight of the formulation.
 4. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present up to 25% by weight of the formulation.
 5. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present up to 10% by weight of the formulation.
 6. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present up to 5% by weight of the formulation.
 7. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present from about 1.25 to 20 mg/mL in the formulation.
 8. The formulation of claim 1, wherein the 9-cis-retinyl acetate is present at about 20 mg/mL in the formulation.
 9. The formulation of claim 1, wherein the anti-oxidant comprises a-tocopherol, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ascorbyl palmitate, propyl gallate, tert-butyl hydroquinone (TBHQ), or a chelating agent, or a combination thereof.
 10. The formulation of claim 1, wherein the anti-oxidant comprises butylated hydroxyanisole (BHA).
 11. The formulation of claim 1, wherein the formulation comprises about 0.1% by weight to volume of the anti-oxidant.
 12. The formulation of claim 1, wherein the 11-cis-retinal deficiency is due to an RPE65 mutation.
 13. The formulation of claim 1, wherein the 11-cis-retinal deficiency is due to an LRAT mutation.
 14. The formulation of claim 1, wherein the human subject has Leber congenital amaurosis (LCA).
 15. The formulation of claim 1, wherein the human subject has Retinitis Pigmentosa (RP).
 16. The formulation of claim 1, wherein the formulation is configured to provide a dosage of about 1.25-40 mg/m² of the 9-cis-retinyl acetate by body surface area to the subject.
 17. The formulation of claim 1, wherein the formulation is configured to provide a dosage of about 40 mg/m² of the 9-cis-retinyl acetate by body surface area to the subject.
 18. The formulation of claim 1, wherein the formulation is in the form of an oil-in-water emulsion.
 19. The formulation of claim 1, wherein the formulation is configured for single dosing, intermittent dosing or daily dosing.
 20. The formulation of claim 1, wherein the formulation is packaged in an amber container. 